For example, in display devices that display a color image, which are represented by projectors and projection TVs, light sources of, for example, three colors R (red), G (green) and B (blue) are needed as light sources.
In recent years, as these light sources, there has been proposed a laser device of wavelength conversion type that provides, as fundamental waves, laser lights whose fundamental wavelengths fall within a 900 nm band, a 1 μm band or a 1.3 μm band, respectively (the fundamental waves are referred to as fundamental wave laser lights from here on), and that performs wavelength conversion on these fundamental waves laser lights by using a nonlinear material to cause second harmonic generation (SHG), thereby generating lights having needed colors (wavelengths).
As an example of such a conventional laser device, there is a laser device which is comprised of a semiconductor laser, a laser medium and a nonlinear material.
(Patent Reference 1)
A laser device disclosed in patent reference 1 includes a semiconductor laser, a laser medium and a non-linear optical material as components associated with generation of a laser light, as shown in FIG. 1 in patent reference 1.
The semiconductor laser element generates a pumping light for the laser medium. The generated pumping light is absorbed by the laser medium, and a gain for amplifying a fundamental wave laser light is generated in the laser medium.
In addition, by virtue of the generated gain, laser oscillation occurs at a fundamental wavelength in the laser medium and a fundamental wave laser light is emitted. The fundamental wave laser light emitted from the laser medium is converted into a light which is a second harmonic wave through the wavelength conversion in the non-linear optical material.